The present invention relates to an integral porous membrane comprising an amorphous halopolymer in general, and, in particular, to an integral porous membrane comprising an amorphous fluoropolymer, a process for preparing such a membrane, and a process for treating fluids by using such a membrane.
The treatment of corrosive or reactive fluids such as sulfuric acid and hydrofluoric acid has been a challenge to the industry, particularly to the separation/filtration industry. Although halopolymers, particularly fluoropolymers, have significant resistance to many chemicals, solvents, as well as corrosive fluids, halopolymer membranes or filters are of limited availability, due in part, to the inherent properties of the halopolymers. Many halopolymers, particularly, fluoropolymers, have a limited solubility in solvents suitable for preparing membranes. Alternatively, the halopolymers have very high melting points, decompose at elevated temperatures, and/or involve complex processes for converting them into membranes.
A composite membrane has been proposed wherein an amorphous fluoropolymer is disposed as a surface treatment or coating on the pore walls of a porous substrate. This membrane is not satisfactory for many applications because, for example, it may fail to provide the desired filtration efficiency and/or the membrane lacks solvent and chemical resistance, e.g., due to the poor solvent and/or chemical resistance of some porous substrates. The layers constituting certain composite membranes also tend to delaminate, for example, under use or cleaning conditions. Thus, there exists a need for a porous halopolymer membrane that is suitable for treating corrosive or reactive fluids.
The advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein
The foregoing need has been fulfilled by the present invention which provides an integral porous membrane comprising an amorphous halopolymer. The amorphous halopolymer constitutes the bulk or body of the membrane rather than merely being disposed as a surface treatment or coating an a porous material.
The present invention further provides processes for preparing the integral porous membrane. The membrane is preferably prepared by a process comprising casting a solution of the halopolymer and causing phase inversion to occur. The present invention further provides devices comprising the membrane and processes for treating fluids.
While the invention has been described and disclosed below in connection with certain embodiments and procedures, it is not intended to limit the invention to those specific embodiments. Rather it is intended to cover all such alternative embodiments and modifications as fall within the scope of the invention.